I have never has chickens before but a friend gave us the 2 they had because the neighbors didn't like them. So what I need to know is; I have food grade Fossil DE, that I use in the garden for pest control. Can I use it in a coop with shaved pine, in there nesting box and in a dusting box? Also when do they start laying. They said they were around 3 1/2 to 4 months old when we got them. Our local mill sold me layer feed and said they should start laying around 21 weeks.